re-land: Track history of events in GCTracer.

re-land: Track history of events in GCTracer.

- track incremental marking stats directly on GCTracer.
- add simple ring buffer class.
- track last 10 scavenges and mark-compacts in ring buffers on GCTracer.
- various clean-ups.

This is a re-land of https://codereview.chromium.org/391413006/ with
 - int instead of size_t in ring buffer unit test.
 - git cl format

R=hpayer@chromium.org
BUG=

Committed: https://code.google.com/p/v8/source/detail?r=22593

[ernstm, 2014-07-24 08:28:53]

Re-landing with fixed unit tests and git cl format. PTAL.

[Hannes Payer (out of office), 2014-07-24 08:30:56]

lgtm

[Yang, 2014-07-24 11:07:45]

On 2014/07/24 08:30:56, Hannes Payer wrote:
> lgtm

also update BUILD.gn please.

[ernstm, 2014-07-24 11:16:11]

Committed patchset #3 manually as r22593 (presubmit successful).